Internal combustion engine

ABSTRACT

In an internal combustion engine of the type having a timing cam with a distance from center to cam surface with varies along its axis of rotation and at least one cam follower which rides on the cam surface to operate a valve so that the valve operating characteristics vary as a function of the position of the cam follower along the axis of rotation of the cam, the improvement wherein the cam follower includes a ball having a flat surface engaging the cam surface so that a line of contact always exists between the ball and the cam surface and means for mounting said ball in the follower, producing a mechanism which is durable, cheap to manufacture and adaptable to present day engines.

United States Patent 1191 Rust et a1. 5] Oct. 28, 1975 INTERNALCOMBUSTION ENGINE [76] Inventors: Robert H. Rust, 1073 Hampton Z"',"f gf 3 Road, Daytona Beach, Fla. 32014; & Leonard Owen Fulghum, 26 63rdAttorney, Agent, or Fzrm-Cus man, ar y St., Savannah, Ga. 31405 Cushman[22] Filed: Sept. 18, 1974 57 ABSTRACT [21] Appl. No.: 507,240 In aninternal combustion engine of the type having a timing cam with adistance from center to cam surface with varies along its axis ofrotation and at least one l23l90.lli%ll4/l5gz cam follower which rideson the cam surface to oper d 0 2 90/16 ate a valve so that the valveoperating characteristics o 15 9O vary as a function of the position ofthe cam follower along the axis of rotation of the cam, the improvement56 R f Ct d wherein the cam follower includes a ball having a flat 1 eerences l 6 surface engaging the cam surface so that a line of UNITEDSTATES PATENTS contact always exists between the ball and the cam1,729,448 9/1929 Michell 74/569 surface and means for mounting said ballin the fol- 2,l5l,832 39 ug i---. 74/569 lower, producing a mechanismwhich is durable, 3,270,726 9/1966 Cott0n.... 74/569 heap to manufactureand adaptable to present day 3,523,465 8/1970 Harre11.... 123/9018engines 3,730,150 5/1973 Codner l23/90.l8

1215,7515 2/1924 Michell 74/569 1 Claim, 2 Drawing Figures I zzairt'"US. Patent Oct. 28, 1975 3,915,129

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INTERNAL COMBUSTION ENGINE BRIEF DESCRIPTION OF THE PRIOR ART ANDSUMMARY OF THE INVENTION The invention relates to an improved internalcombustion engine of the type having a timing cam and a cam followerwhich rides on the cam surface to operate a valve.

Heretofore, one of the major compromises affecting the performance of anautomobile engine has been valve timing, duration and lift (generallyreferred to as TDL). Valve TDL determines to a large extend thesmoothness and power characteristics of an engine at various RPMs. Withconventional engines, due to valve TDL, an engine with a smooth idle isunfortunately limited in its power production at high RPM. Conversely,an engine that produces optimum power at high RPM lacks smoothness andtractability at lower speeds. The reason for this problem is that thebreathing characteristics of the engine, i.e., the ability of the engineto draw in a full charge of air-gas mixture into the cylinder and, aftercombustion, to reject the spent exhaust gasses, changes with engine RPM.In conventional engines, however, the valve TDL is fixed while thebreathing characteristics of the engine change with RPM. Accordingly,the valve TDL is conventionally a compromise to produce relativelysmooth idle with adequate power at high RPMs. This compromise producesneither optimum smoothness at idle nor optimum power at high RPM. I

One possible technique to deal with this problem which has beensuggested in the past is to construct the cam to have a distance fromcenter to cam surface which varies along its axis of rotation. The camfollower can then be shifted along its axis of rotation as a function ofengine speed by centrifugal or other mechanisms so that the cam followerrides on a portion of the cam surface which is optimum for the speed atwhich the engine is rotating. The US. Pat. No. 2,980,089, to Sampietro,is typical of this general type of improved engine.

The primary drawback to improvements of this type in the part is thatthey provide essentially a single point of contact between the camfollower and the cam surface. The most common mechanism in this type ofstructure employs a roller having a rounded contour which enables it tofollow the varying contours of the cam surface.

However, this single point of contact is insufficient for the surfacesof the cam follower and the cam surface to endure the tremendouspressures which result from the inertia in the valve train mechanism. Incontrast with those variable cam arrangements having a point of contact,a conventional lifter has a line of contact of about three-eighths inchwith the conventional surface which permits it to stand up underlongrange operating conditions.

The present invention relates to an improved internal combustion enginein which a cam follower is employed which includes a ball having a flatsurface engaging the cam surface. This engagement results in a line ofcontact which always exists between the ball and the cam surface. Theresult is a mechanism which is simple, durable, cheap to manufacture andeasily adaptable to present day internal combustion engines.

At least two patents in the prior art describes arrangements of thisgeneral type which do not have a single point of contact. The U.S. Pat.No. 3,618,573, to Allen, describes an arrangement in which a universallymounted rocker is used. Such a rocker, however, may not be entirelypractical due to the necessity of the rocker mechanism being subjectedto tremendous lateral acceleration because the entire rocker must followthe contours of the cam lobe. The US. Pat. No. 3,730,150, to Codner,describes a mechanism in which a roller is used and a line of contact isattempted to be maintained at a fixed angle. This fixed angle is notcompatible with varying angles of the cam lobe.

Many other objects and purposes of the invention will be clear from thefollowing detailed description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. ll shows a cut-away view of aportion of an improved internal combustion engine of this invention;

FIG. 2 shows a schematic view of the cam follower and can which comprisethe improvement of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS Reference is now made to FIGS. 1and 2 which illustrate the improvement of this invention. As inconventional internal combustion engines, cam 20 is mounted for rotationwith the engine and the speed of rotation of the timing cam is afunction of the speed of rotation of the engine. Further, cam 20 ismounted in any conventional way so as to be movable along its axis as afunction of the engine RPM. Any conventional mechanism, such as thearrangement which is described in the Allen US. Pat. No. 3,618,573, canbe employed. Centrifugal, hydraulic, electrical or any other mechanismsfor moving the cam shaft can be employed and the way in which that shaftis moved along its axis is not part of the invention of thisapplication.

Also, in the same fashion as in conventional engines, a mechanical camfollower or lifter 22 is mounted for longitudinal movement as it followsthe surface of cam 20. It will, of course, be understood that while theembodiment of this application illustrates a mechanical lifter,hydraulic and other conventional lifters can also be employed in thesame fashion.

However, in contrast with conventional arrangements, the cam follower 22in the embodiment of this invention comprises a ball 24 having a flatsurface 26 which engages the surface of cam 20. As can be seen in FIG.2, cam 20 has a distance between its axis of rotation and its surfacewhich varies along the length of that axis so that, as cam 20 is movedin the direction of the arrows of FIG. 2, the flat surface 26 engagesdifferent portions thereof to change the TDL characteristics of thevalve which is mechanically or otherwise connected to the lifter 22. Byusing a ball having a flat surface, a continuous line of contact alwaysexists between the ball and the cam surface and this results in amechanism which is practical, durable, cheap to manufacture andadaptable to present day engines.

Many changes and modifications in the above described embodiment of theinvention can, of course, be carried out without departing from thescope thereof. Accordingly, that scope is intended to be limited only bythe scope of the appended claims.

What is claimed is:

1. In an internal combustion engine of the type having a timing cam witha distance from center to cam having a flat surface engaging the camsurface so that a line of contact always exists between the ball and thecam surface and means for mounting said ball in said follower.

1. In an internal combustion engine of the type having a timing cam witha distance from center to cam surface which varies Along its axis ofrotation and at least one cam follower which rides on said cam surfaceto operate a valve so that the valve operating characteristics vary as afunction of the position of the cam follower along the axis of rotationof the cam, the improvement wherein the cam follower includes a ballhaving a flat surface engaging the cam surface so that a line of contactalways exists between the ball and the cam surface and means formounting said ball in said follower.